Piezoelectric Cooling Fan

ABSTRACT

A piezoelectric cooling fan comprises a support frame and two piezoelectric actuators. Each piezoelectric actuator includes an electrical-conductive plate and a piezoelectric plate attached to the electrical-conductive plate, wherein an edge portion of the electrical-conductive plate is fixedly attached to a base of the support frame and approximately aligned with an edge portion of the piezoelectric plate attached thereto. The two piezoelectric actuators are symmetrically arranged with respect to the base of the support frame to define a cavity therebetween and are electrically connected with an AC power source, so that the piezoelectric actuators can be driven to flex towards and away from each other with respect to the edge portions of the piezoelectric actuators, so that air pulses can be induced from the cavity between the piezoelectric actuators for heat dissipation. The piezoelectric cooling fan is light, compact, low noise, low power, and free of electromagnetic interference.

(a) TECHNICAL FIELD OF THE INVENTION

The present invention relates to a piezoelectric cooling fan and, moreparticular, to a cooling fan which does not employ a rotary motor andcan achieve a design that is light, compact, low noise, low power, andfree of electromagnetic interference.

(b) DESCRIPTION OF THE PRIOR ART

FIGS. 1 and 1A show a conventional cooling fan 2, which is driven by amotor. For example, U.S. Pat. No. 7,165,938 B2 and US. PublicationNumber 2008/0130226 A1 belong to this type of cooling fan. Sinceportable electronic products, such as notebook or tablet pc, becomesmaller and smaller, the conventional cooling fan 2 has been challengedby space issues. To effectively reduce the thickness of a cooling fan isan important task that all manufacturers of cooling fan should face.

Based on long-term experience of related works and constant test andinnovation, the applicant has contrived a piezoelectric cooling fan thatis light, compact, low noise, low power, and free of electromagneticinterference.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide apiezoelectric cooling fan that employs slim piezoelectric actuators andcan achieve a design that is light, compact, low noise, low power, andfree of electromagnetic interference.

To achieve the above object, the piezoelectric cooling fan may comprisea support frame and two piezoelectric actuators. Each piezoelectricactuator includes an electrical-conductive plate and a piezoelectricplate attached to the electrical-conductive plate, wherein an edgeportion of the electrical-conductive plate is fixedly attached to a baseof the support frame and approximately aligned with an edge portion ofthe piezoelectric plate attached thereto. The two piezoelectricactuators are symmetrically arranged with respect to the base of thesupport frame to define a cavity therebetween and are electricallyconnected with an AC power source, so that the piezoelectric actuatorscan be driven to flex towards and away from each other with respect tothe edge portions of the electrical-conductive plates and thepiezoelectric plates, so that air pulses can be induced from the cavitybetween the piezoelectric actuators for heat dissipation.

According to one aspect of the present invention, the piezoelectriccooling fan may further comprise two protective covers beingrespectively placed over the piezoelectric plates and mounted to thesupport frame.

In operation, when the piezoelectric actuators are energized with an ACpower source, the remaining portions other than the edge portions of theelectrical-conductive plates and the piezoelectric plate can be drivento flex towards and away from each other with respect to the edgeportions of the electrical-conductive plates and the piezoelectricplates, so that air pulses can be induced from the cavity between thepiezoelectric actuators for heat dissipation. The piezoelectric coolingfan can achieve a design that is light, compact, low noise, low power,and free of electromagnetic interference.

Other objects, advantages, and novel features of the present inventionwill become more apparent from the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a 3-dimensional view of a conventional cooling fan.

FIG 1A shows a sectional view of the conventional cooling fan takenalong line A-A in FIG. 1.

FIG. 2 shows a 3-dimensional view of a piezoelectric cooling fanaccording to one embodiment of the present invention.

FIG. 3 shows an exploded view of the embodiment of the presentinvention.

FIG. 4 shows a top view of the embodiment of the present invention.

FIG. 5 shows various sectional views of the embodiment of the presentinvention, wherein one view illustrates that the piezoelectric actuatorsthereof are flexed away from each other for sucking in airflow whereasanother view illustrates that the piezoelectric actuators thereof areflexed towards each other for forcing out airflow.

FIG. 6 shows an exploded view of one of the piezoelectric actuators usedin the present invention.

FIG. 7 shows a 3-dimensional view of one of the piezoelectric actuatorsused in the present invention.

FIG. 8 shows a 3-dimensional view of the embodiment of the presentinvention that further includes two protective covers.

FIG. 9 shows an exploded view of the embodiment of the present inventionthat further includes two protective covers.

FIG. 10 shows a top view of the embodiment of the present invention thatfurther includes two protective covers.

FIG. 11 shows a sectional view (taken along line A-A in FIG. 10) of theembodiment of the present invention that further includes two protectivecovers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To allow the features and advantages of the present invention to befully understood, one embodiment of the present invention is illustratedin the following paragraphs with reference to the accompanying drawings.

FIGS. 2 through 7 show a piezoelectric cooling fan according to oneembodiment of the present. As shown, the piezoelectric cooling fangenerally comprises a support frame 11 and two piezoelectric actuators12. Each piezoelectric actuator 12 includes an electrical-conductiveplate 121 and a piezoelectric plate 122 attached to theelectrical-conductive plate 121, wherein an edge portion of theelectrical-conductive plate 121 is fixedly attached to a base of thesupport frame 11 and approximately aligned with an edge portion of thepiezoelectric plate 122 attached thereto. The two piezoelectricactuators 12 are symmetrically arranged with respect to the base of thesupport frame 11 to define a cavity therebetween. Furthermore, the twopiezoelectric actuators 12 are electrically connected with an AC powersource (not shown) through a pair of electrical wires, so that thepiezoelectric actuators 12 can be driven to flex towards and away fromeach other with respect to the edge portions of theelectrical-conductive plates 121 and the piezoelectric plates 122, sothat air pulses can be induced from the cavity between the piezoelectricactuators 12 for heat dissipation. One of the electrical wires can be aneutral wire that are electrically connected to theelectrical-conductive plates 121 whereas the other one of the electricalwires can be a live wire that are electrically connected to thepiezoelectric plates 122 on the electrical-conductive plates 121.

As shown in FIG. 6, the electrical-conductive plates 121 and thepiezoelectric plates 122 are rectangular. Because the edge portions ofthe plates 121, 122 are fixed to the base of the support frame 11, theeffective length (or the remaining length) of the electrical-conductiveplates 121 and the piezoelectric plates 122 is less than their originallength. As shown, each electrical-conductive plate 121 has a length ofLm, an effective length of Lme, and an effective width of Wme; eachpiezoelectric plate 122 has a length of Lc, an effective length of Lce,and an effective width of Wce; wherein the ratio of Lce to Lme is lessthan or equal to 1.0 and is greater than or equal to 0.1; the ratio ofWce to Wme is less than or equal to 1.0 and is greater than or equal to0.5. Preferably, the above ratios can be further limited to allow thepiezoelectric cooling fan to have an optimal performance, wherein theratio of Lce to Lme is less than or equal to 0.6 and is greater than orequal to 0.4; the ratio of Wce to Wme is less than or equal to 1.0 andis greater than or equal to 0.96. Furthermore, the support frame 11 canbe made of metal, plastic, engineering plastic, ceramic, or compositematerial. The electrical-conductive plates 121 can be made of metal orcomposite material with electrical conductivity.

In operation, when the piezoelectric actuators 12 are energized with anAC power source, the remaining portions other than the edge portions ofthe electrical-conductive plates 121 and the piezoelectric plates 122will be driven to flex towards and away from each other with respect tothe edge portions of the electrical-conductive plates 121 and thepiezoelectric plates 122, so that air pulses can be induced from thecavity between the electrical-conductive plates 122 for heatdissipation. As shown in FIG. 5, when the piezoelectric actuators 12 areflexed away from each other, airflow can be sucked into the cavitybetween the piezoelectric actuators 12 (see right figure). On the otherhand, when the piezoelectric actuators 12 are flexed towards each other,airflow can be forced out from the cavity (see left figure). To design apiezoelectric cooling fan with a proper flow rate and a reduced noiselevel is determined by the dimension of the cavity between the twopiezoelectric actuators 12. In an experiment, a piezoelectric coolingfan according to the embodiment of the present invention isinvestigated, wherein the cooling fan has an outside dimension of 40 mm(length)×40 mm (width)×3 mm (thickness), the area of the cavity exit ofthe cooling fan is about 35 mm×1.3 mm=45.5 square-mm, and the AC powersource for the cooling fan is an electrical power of 30 volts at 200 HZ.The measurement of the flow rate of the airflow from the cavity canreach 1.0 cubic-meter per minute. This amount of the airflow inducedfrom the cavity is adequate for dissipating the heat generated from aCPU. The noise level measured at a distance of 30 cm from the coolingfan is about 30 dB. In the experiment, the associated parameters of theelectrical-conductive plate 121 is: Lm=34 mm, Lme=28 mm; the associatedparameters of the piezoelectric plate 122 is: Lc=18 mm; the ratio of Lceto Lme is 0.5 (14:28); the ratio of Wce to Wme is 0.96. The electricalcurrent required for the cooling fan is about 7 mA, and thus the powerconsumption is about 30 volts×7 mA, which is equal to 0.21W, and thusthe fan is a power-saving device.

FIGS. 8 through 11 show the embodiment of the present invention thatfurther includes two protective covers 13 a being respectively placedover the two piezoelectric actuators 12 a and mounted to the supportframe 11 a. Specifically, the two protective covers 13 a are placed overthe piezoelectric plates of the piezoelectric actuators 12 arespectively. The protective covers 13 a, which can be made of resin,paper, or composite material, are used to protect the piezoelectricplates of the piezoelectric actuators 12 a from being touched.

As a summary, the piezoelectric cooling fan of the present invention canachieve a design that is light, compact, low noise, low power, and freeof electromagnetic interference. Therefore, the present invention is auseful creation.

Although the present invention has been described with a certain degreeof particularity, it is understood that the present disclosure is madeby way of example only and the combination and arrangement of parts maybe resorted to without departing from the spirit and scope of theinvention hereinafter claimed.

I claim:
 1. A piezoelectric cooling fan, comprising: a support frame,and two piezoelectric actuators each including an electrical-conductiveplate and a piezoelectric plate attached to the electrical-conductiveplate, wherein an edge portion of the electrical-conductive plate isfixedly attached to a base of the support frame and approximatelyaligned with an edge portion of the piezoelectric plate attachedthereto, the two piezoelectric actuators being symmetrically arrangedwith respect to the base of the support frame to define a cavitytherebetween and being electrically connected with an AC power source,so that the piezoelectric actuators can be driven to flex towards andaway from each other with respect to the edge portions of theelectrical-conductive plates and the piezoelectric plates, so that airpulses can be induced from the cavity between the piezoelectricactuators for heat dissipation.
 2. The piezoelectric cooling fan ofclaim 1, further comprising two protective covers being respectivelyplaced over the piezoelectric plates and mounted to the support frame 3.The piezoelectric cooling fan of claim 2, wherein the protective coversare made of resin, paper, or composite material.
 4. The piezoelectriccooling fan of claim 1, wherein each electrical-conductive plate isrectangular and has a length of Lm, an effective length of Lme, and aneffective width of Wme; each piezoelectric plate is rectangular and hasa length of Lc, an effective length of Lce, and an effective width ofWee; wherein the ratio of Lce to Lme is less than or equal to 1.0 and isgreater than or equal to 0.1; the ratio of Wce to Wme is less than orequal to 1.0 and is greater than or equal to 0.5., and wherein all theratios are further limited such that the ratio of Lee to Lme is lessthan or equal to 0.6 and is greater than or equal to 0.4; the ratio ofWce to Wme is less than or equal to 1.0 and is greater than or equal to0.96.
 5. The piezoelectric cooling fan of claim 1, wherein the supportframe is made of metal, plastic, engineering plastic, ceramic, orcomposite material.
 6. The piezoelectric cooling fan of claim 1, whereinthe electrical-conductive plates are made of metal or composite materialwith electrical conductivity